Base station and related radio communication method

ABSTRACT

Provided are a terminal device and a retransmission control method that make it possible to minimize increases in overhead in an uplink control channel (PUCCH), even if channel selection is used as the method to transmit response signals during carrier-aggregation communication using a plurality of downlink unit bands. On the basis of the generation status of uplink data and error-detection results obtained by a CRC unit, a control unit in the provided terminal uses response signal transmission rules to control the transmission of response signals or uplink control signals that indicate the generation of uplink data. If an uplink control signal and a response signal are generated simultaneously within the same transmission time unit, the control unit changes the resources allocated to the response signal and/or the phase point of the response signal in accordance with the number and position of ACKs within the error-detection result pattern.

TECHNICAL FIELD

The present invention relates to a terminal apparatus and aretransmission control method.

3GPP long term evolution (LTE) adopts orthogonal frequency divisionmultiple access (OFDMA) as a downlink communication scheme. In a radiocommunication system to which 3GPP LTE is applied, a base stationtransmits a synchronization signal (synchronization channel: SCH) and abroadcast signal (broadcast channel: BCH) using predeterminedcommunication resources. A terminal first secures synchronization withthe base station by catching an SCH. Then, the terminal acquiresparameters (e.g. frequency bandwidth) specific to the base station byreading BCH information (see Non-Patent Literatures 1, 2, and 3).

Furthermore, after completing the acquisition of the parameters specificto the base station, the terminal transmits a connection request to thebase station and establishes communication with the base station. Thebase station transmits control information to the terminal with whichcommunication is established through a physical downlink control channel(PDCCH) as necessary.

The terminal then makes a “blind decision” on each of a plurality ofpieces of control information included in the received PDCCH signal.That is, the control information includes a cyclic redundancy check(CRC) portion, and this CRC portion is masked with a terminal ID of atransmission target terminal in the base station. Therefore, theterminal is difficult to decide whether or not the control informationis directed to its own terminal until the CRC portion of the receivedcontrol information is demasked with the terminal ID of the terminal. Inthe blind decision, when a demasking result represents that a CRCcalculation is OK, it is determined that the control information isdirected to its own terminal.

Furthermore, in 3GPP LTE, automatic repeat request (ARQ) is applied todownlink data from a base station to a terminal. That is, the terminalfeeds back a response signal indicating an error detection result ofdownlink data to the base station. The terminal performs a CRC on thedownlink data, and feeds back acknowledgment (ACK) when CRC=OK (noerror) and negative acknowledgment (NACK) when CRC=NG (error) to thebase station as a response signal. A binary phase shift keying (BPSK)scheme is used for modulation of the response signal (that is, theACK/NACK signal). Further, an uplink control channel such as a physicaluplink control channel (PUCCH) is used for feedback of the responsesignal. When the received response signal represents NACK, the basestation transmits retransmission data to the terminal.

Here, the control information transmitted from the base station includesresource assignment information including resource information and thelike assigned from the base station to the terminal. The PDCCH is usedfor transmission of this control information as described above. ThePDCCH is configured with one or more L1/L2 control channels (L1/L2CCHs). Each L1/L2 CCH is configured with one or more control channelelements (CCEs). That is, a CCE is a base unit for mapping controlinformation to a PDCCH. Furthermore, when one L1/L2 CCH is configuredwith a plurality of CCEs, a plurality of CCEs whose indices areconsecutive are assigned to the L1/L2 CCH. The base station assigns anL1/L2 CCH to a resource assignment target terminal according to thenumber of CCEs necessary for notifying control information to theresource assignment target terminal. The base station then transmits thecontrol information mapped to a physical resource corresponding to theCCE of the L1/L2 CCH.

Here, each CCE has a one-to-one correspondence with a component resourceof the PUCCH. Therefore, the terminal that has received the L1/L2 CCHcan implicitly specify a component resource of the PUCCH correspondingto the CCEs configuring the L1/L2 CCH, and transmits a response signalto the base station using the specified resource. This allows downlinkcommunication resources to be used efficiently.

As illustrated in FIG. 1, a plurality of response signals transmittedfrom a plurality of terminals are spread by a Zero Auto-correlation(ZAC) sequence having a Zero Auto-correlation characteristic, a Walshsequence, and a discrete Fourier transform (DFT) sequence on a timeaxis, and code-multiplexed within the PUCCH. In FIG. 1, (W₀, W₁, W₂, W₃)represents a Walsh sequence (which may be also referred to as “Walshcode sequence” or “Walsh code”) having a sequence length of 4, and (F₀,F₁, F₂) represents a DFT sequence having a sequence length of 3. Asillustrated in FIG. 1, in the terminal, a response signal of ACK or NACKis first primary-spread to frequency components corresponding to a onesingle carrier frequency division multiple access (1 SC-FDMA) symbol ona frequency axis by a ZAC sequence (having a sequence length of 12).Next, the response signal subjected to the primary spreading and the ZACsequence functioning as a reference signal are secondary-spread inassociation with a Walsh sequence (having a sequence length 4: W₀ to W₃)and a DFT sequence (having a sequence length 3: F₀ to F₂) respectively.

Further, the signal subjected to the second spreading is transformedinto a signal having a sequence length of 12 on the time axis by theinverse fast Fourier transform (IFFT). Then, a cyclic prefix (CP) isadded to the signal that has been subjected to the IFFT, and thus aone-slot signal including 7 SC-FDMA symbols is generated.

Here, response signals transmitted from different terminals are spreadusing sequences corresponding to different cyclic shift indices ororthogonal cover (OC) indices (that is, a set of a Walsh sequence and aDFT sequence). Therefore, the base station can demultiplex a pluralityof code-multiplexed response signals using a conventional dispreadingprocess and a conventional correlation process (see Non-PatentLiterature 4).

However, since each terminal makes a blind decision on a downlinkassignment control signal in each subframe directed to its own terminal,the terminal side does not necessarily succeed in receiving the downlinkassignment control signal. When the terminal fails to receive thedownlink assignment control signal directed to its own terminal in acertain downlink unit band, the terminal is difficult to know whether ornot there is downlink data, directed to its own terminal, in thedownlink unit band. Therefore, when failing to receive the downlinkassignment control signal in a certain downlink unit band, the terminalis difficult to generate a response signal on the downlink data in thedownlink unit band. This error case is defined as discontinuoustransmission (DTX) of a response signal (DTX of ACK/NACK signals) in thesense that the terminal side does not transmit the response signal.

Meanwhile, the uplink control channel (PUCCH) is also used fortransmission of a scheduling request (SR) (which may be also representedby a scheduling request indicator (SRI)) which is an uplink controlsignal indicating that uplink data to be transmitted from the terminalside has been generated. When a connection with the terminal has beenestablished, the base station individually assigns a resource to be usedfor transmission of the SR (hereinafter, referred to as “SR resource”)to each terminal. Further, an on-off keying (00K) scheme is applied tothe SR, and the base station detects the SR from the terminal based onwhether or not the terminal is transmitting an arbitrary signal usingthe SR resource. Further, the SR is spread using a ZAC sequence, a Walshsequence, and a DFT sequence in the same manner as the above-mentionedresponse signal.

In the LTE system, the SR and the response signal may be generated inthe same sub frame. In this case, when the terminal code-multiplexes andtransmits the SR and the response signal, a peak to average power ratio(PAPR) of a synthesized waveform of a signal transmitted from theterminal significantly deteriorates. However, in the LTE system, sinceimportance is put on amplification efficiency of the terminal, when theSR and the response signal have been generated in the same sub frame atthe terminal side, the terminal transmits the response signal (responsesignals illustrated in FIGS. 2A to 2D) using the SR resource previouslyindividually assigned to each terminal, without using a resource(hereinafter, referred to as “ACK/NACK resource”) used for transmissionof the response signal as illustrated in FIG. 2A.

That is, when the terminal side has only to transmit only a responsesignal (“when only response signal is transmitted” illustrated in FIG.2C), the terminal transmits the response signal (a response signalillustrated in FIG. 2C) using the ACK/NACK resource. On the other hand,when the SR and the response signal have been generated in the same subframe at the terminal side (“when response signal and SR aretransmitted” illustrated in FIG. 2D), the terminal transmits theresponse signal (a response signal illustrated in FIG. 2D) using the SRresource.

Thus, the PAPR of the synthesized waveform of the signal transmittedfrom the terminal can be reduced. At this time, the base station detectsthe SR from the terminal based on whether or not the SR resource isbeing used. In addition, the base station determines whether or not theterminal has transmitted either ACK or NACK, based on a phase (that is,a BPSK demodulation result) of a signal transmitted through the SRresource (the ACK/NACK resource when the SR resource is not used).

Further, the standardization of 3GPP LTE-advanced that realizes fastercommunication than 3GPP LTE has started. A 3GPP LTE-advanced system(which may also be hereinafter referred to as “LTE-A system”) followsthe 3GPP LTE system (which may also be hereinafter referred to as “LTEsystem”). In order to realize a downlink transmission rate of a maximumof 1 Gbps or above, 3GPP LTE-advanced is expected to introduce basestations and terminals capable of performing communication at a widebandfrequency of 40 MHz or above.

In an LTE-A system, in order to simultaneously realize communication atan ultra-high transmission rate several times as fast as a transmissionrate in the LTE system and backward compatibility with the LTE system, aband for the LTE-A system is divided into “unit bands” of 20 MHz orless, which is a support bandwidth for the LTE system. That is, the“unit band” herein is a band having a width of maximum 20 MHz anddefined as a base unit of a communication band. Furthermore, a “unitband” in a downlink (hereinafter, referred to as “downlink unit band”)may be defined as a band divided by downlink frequency band informationincluded in the BCH broadcasted from the base station, or a band definedby a dispersive width when the downlink control channel (PDCCH) isdispersed and arranged in the frequency domain. Further, a “unit band”in an uplink (hereinafter, referred to as “uplink unit band”) may bedefined as a band divided by uplink frequency band information includedin the BCH broadcasted from the base station, or as a base unit of acommunication band of 20 MHz or less, which includes a physical uplinkshared channel (PUSCH) region near the center thereof and PUCCHs for theLTE at both ends thereof. Furthermore, in 3GPP LTE-Advanced, the “unitband” may also be expressed as “component carrier(s)” in English.

The LTE-A system supports communication using a band that bundlesseveral unit bands, so-called “carrier aggregation.” Since throughputrequirements for an uplink are generally different from throughputrequirements for a downlink, in the LTE-A system, carrier aggregation inwhich the number of unit bands set for a terminal supporting arbitraryLTE-A system (hereinafter referred to as “LTE-A terminal”) is differentbetween the uplink and the downlink, so-called “asymmetric carrieraggregation” is being discussed. Cases are also supported where thenumber of unit bands is asymmetric between the uplink and the downlink,and different unit bands have different frequency bandwidths.

FIGS. 3A and 3B are diagrams illustrating asymmetric carrier aggregationapplied to individual terminals and a control sequence thereof. FIGS. 3Aand 3B illustrates an example in which a bandwidth and the number ofunit bands are symmetric between an uplink and a downlink in a basestation.

In FIG. 3B, a setting (configuration) is made for terminal 1 such thatcarrier aggregation is performed using two downlink unit bands and oneuplink unit band on the left side, whereas a setting is made forterminal 2 such that although the two same downlink unit bands as thosein terminal 1 are used, the uplink unit band on the right side is usedfor uplink communication.

Focusing attention on terminal 1, signals are transmitted/receivedbetween an LTE-A base station and an LTE-A terminal configuring an LTE-Asystem according to a sequence diagram illustrated in FIG. 3B. Asillustrated in FIG. 3A, (1) terminal 1 is synchronized with the downlinkunit band (DL CC1) on the left side illustrated in FIG. 3B whencommunication with the base station starts, and reads information of theuplink unit band which forms a pair with the downlink unit band on theleft side from a broadcast signal called “system information block type2 (SIB2).” (2) Using this uplink unit band (UL CC1), terminal 1 startscommunication with the base station by transmitting, for example, aconnection request to the base station. (3) Upon deciding that aplurality of downlink unit bands need to be assigned to the terminal,the base station instructs the terminal to add a downlink unit band (DLCC2). In this case, however, the number of uplink unit bands does notincrease, and terminal 1 which is an individual terminal startsasymmetric carrier aggregation.

Furthermore, in the LTE-A to which the carrier aggregation is applied, aterminal may receive a plurality of downlink data in a plurality ofdownlink unit bands at a time. In the LTE-A, a channel selection (whichmay be also referred to as “multiplexing” or “code selection”) is beingdiscussed as one of methods of transmitting a plurality of responsesignals in response to the plurality of downlink data. In the channelselection, not only a symbol used for a response signal but also aresource to which the response signal is mapped are changed according toa pattern of an error detection result on the plurality of downlinkdata. That is, the channel selection is a technique that changes notonly a phase point (that is, a constellation point) of the responsesignal but also a resource used for transmitting the response signalbased on whether each of response signals in response to a plurality ofdownlink data received in a plurality of downlink unit bands is ACK orNACK as illustrated in FIG. 4 (see Non-Patent Literatures 5, 6, and 7).

Here, ARQ control based on the channel selection when theabove-described asymmetric carrier aggregation is applied to a terminalwill be described below with reference to FIG. 4.

For example, as illustrated in FIG. 4, when a unit band group (which maybe expressed as “component carrier set” in English) configured withdownlink unit bands 1 and 2 and uplink unit band 1 is set for terminal1, downlink resource assignment information is transmitted from the basestation to terminal 1 through respective PDCCHs of downlink unit bands 1and 2, and then downlink data is transmitted using a resourcecorresponding to the downlink resource assignment information.

When the terminal succeeds in receiving the downlink data at unit band 1and fails to receive the downlink data at unit band 2 (that is, when aresponse signal of unit band 1 is ACK and a response signal of unit band2 is NACK), the response signal is mapped to a PUCCH resource includedin PUCCH region 1, and a first phase point (e.g. a phase point (1, 0))is used as a phase point of the response signal. Further, when theterminal succeeds in receiving the downlink data at unit band 1 and alsosucceeds in receiving the downlink data at unit band 2, the responsesignal is mapped to a PUCCH resource included in PUCCH region 2, and thefirst phase point is used. That is, when there are two downlink unitbands, there are four error detection result patterns, so that the fourpatterns can be represented by combinations of two resources and twotypes of phase points.

CITATION LIST Patent Literature NPL 1

-   3GPP TS 36.211 V8.7.0, “Physical Channels and Modulation (Release    8),” May 2009

NPL 2

-   3GPP TS 36.212 V8.7.0, “Multiplexing and channel coding (Release    8),” May 2009

NPL 3

-   3GPP TS 36.213 V8.7.0, “Physical layer procedures (Release 8),” May    2009

NPL 4

-   Seigo Nakao, Tomofumi Takata, Daichi Imamura, and Katsuhiko    Hiramatsu, “Performance enhancement of E-UTRA uplink control channel    in fast fading environments,” Proceeding of IEEE VTC 2009 spring,    April. 2009

NPL 5

-   ZTE, 3GPP RANI meeting #57 bis, R1-092464, “Uplink Control Channel    Design for LTE-Advanced,” June 2009

NPL 6

-   Panasonic, 3GPP RANI meeting #57bis, R1-092535, “UL ACK/NACK    transmission on PUCCH for carrier aggregation,” June 2009

NPL 7

-   Nokia Siemens Networks, Nokia, 3GPP RANI meeting #57bis, R1-092572,    “UL control signalling for carrier aggregation,” June 2009

SUMMARY OF INVENTION Technical Problem

As described above, the SR resource and the ACK/NACK resource have thesame format, and when the SR and the response signal are simultaneouslytransmitted, the terminal transmits the response signal using the SRresource. Here, when the channel selection is applied in the LTE-Asystem as a method of transmitting the response signal, the ACK/NACKresources the number of which is equal to the number of downlink unitbands set to the terminal (2 ACK/NACK resources in FIG. 4) are used asdescribed above. Further, when the same technique (that is, a techniqueof transmitting the SR according to which of the SR resource and theACK/NACK resource is used) as in the LTE is used in the LTE-A system soas to simultaneously transmit the SR and the response signal, the SRresources the number of which is equal to the number of the ACK/NACKresources are necessary.

That is, as illustrated in FIG. 5A, in the case in which the channelselection is applied using the two ACK/NACK resources, when the sametechnique as in the LTE is used to simultaneously transmit the SR andthe response signal, the two SR resources the number of which is equalto the number of the ACK/NACK resources are necessary. For example, whenthe terminal does not generate the SR and transmits only the responsesignal (“when only response signal is transmitted” illustrated in FIG.5B), the terminal contains information as to not only a symbol (i.e., aphase point) used for the response signal but also which one of the twoACK/NACK resources (PUCCH regions 1 and 2 in FIG. 4) the response signalhas been mapped to, and then transmits a signal (the response signal).On the other hand, when the terminal has generated the SR and theresponse signal in the same sub frame (“when response signal and SR aretransmitted” illustrated in FIG. 5C), the terminal contains informationas to not only a symbol (i.e., a phase point) used for the responsesignal but also which one of the two SR resources the response signalhas been mapped to, and then transmits a signal (the response signal).

Thus, the base station can recognize a generation status of the SR atthe terminal side by which resources belonging to the “SR resourcegroup” including the two SR resources or the “ACK/NACK resource group”including the two ACK/NACK resources a used. Further, the base stationcan recognize whether or not the terminal has succeeded in receivingdownlink data transmitted in each unit band by a resource belonging tothe resource group used at the terminal side and a phase point of theresource.

As described above, when the channel selection is used, it is necessaryto prepare a plurality of SR resources and a plurality of ACK/NACKresources (two SR resources and two ACK/NACK resources in FIG. 5A).However, as illustrated in FIGS. 5B to 5D, only one PUCCH resource amongthe four PUCCH resources (the two SR resources and the two ACK/NACKresources) is used in a certain sub frame. That is, the three PUCCHresources among the four PUCCH resources are always not used in acertain sub frame.

As described above, when the channel selection is applied in the LTE-Aas a method of transmitting the response signal, if it is considered thecase in which the SR and the response signal are simultaneouslygenerated in the same sub frame, the overhead of the uplink controlchannel (PUCCH) wastefully increases.

It is an object of the present invention to provide a terminal apparatusand a retransmission control method, which are capable of suppressing anincrease in the overhead of the uplink control channel (PUCCH) even whenthe channel selection is applied as method of transmitting the responsesignal when carrier aggregation communication is performed using aplurality of downlink unit bands.

Solution to Problem

A terminal apparatus of the present invention is a terminal apparatusthat communicates with a base station using a unit band group includinga plurality of downlink unit bands and at least one uplink unit band andhas a configuration including a control information receiving sectionthat receives downlink assignment control information corresponding todownlink data transmitted in at least one downlink unit band in the unitband group, a downlink data receiving section that receives downlinkdata corresponding to the downlink assignment control information, anerror detecting section that detects a reception error of the receiveddownlink data, and a control section that transmits an uplink controlsignal representing generation of uplink data or a response signalthrough an uplink control channel of the uplink unit band, using atransmission rule of the response signal, based on a generation statusof the uplink data and an error detection result obtained by the errordetecting section, wherein the transmission rule, when the uplinkcontrol signal and the response signal have been simultaneouslygenerated within a transmission unit time, a pattern candidate of theerror detection result is associated with a pair of a resource of anuplink control channel to which the response signal is assigned and aphase point of the response signal, different pairs are associated withdifferent pattern candidate groups which are different in the number ofACKs included in a pattern, and different pairs are associated withdifferent pattern candidate groups which are the same in the number ofACKs included in a pattern but different in a position of ACK in apattern.

A retransmission control method of the present invention includes acontrol information receiving step of receiving downlink assignmentcontrol information corresponding to downlink data transmitted in atleast one downlink unit band in a unit band group including a pluralityof downlink unit bands and at least one uplink unit band, a downlinkdata receiving step of receiving downlink data corresponding to thedownlink assignment control information, an error detecting step ofdetecting a reception error of the received downlink data, and a controlstep of transmitting an uplink control signal representing generation ofuplink data or a response signal through an uplink control channel ofthe uplink unit band, using a transmission rule of the response signal,based on a generation status of the uplink data and an error detectionresult obtained by the error detecting step, wherein when the uplinkcontrol signal and the response signal have been simultaneouslygenerated within a transmission unit time, the control step includescausing a pair of a resource to which the response signal is assignedand a phase point of the response signal to be different according tothe number of ACKs in an error detection result pattern, and causing apair of a resource to which the response signal is assigned and a phasepoint of the response signal to be different according to a position ofACK in a pattern, when a plurality of error detection result patternshaving the same number of ACKs are present.

Advantageous Effects of Invention

According to the present invention, a terminal apparatus and aretransmission control method can be provided which are capable ofsuppressing an increase in the overhead of the uplink control channel(PUCCH) even when the channel selection is applied as method oftransmitting the response signal when carrier aggregation communicationis performed using a plurality of downlink unit bands.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a method of spreading a response signaland reference signal;

FIGS. 2A to 2D are diagrams for describing a method of transmitting anSR and a response signal by a terminal;

FIGS. 3A and 3B are diagrams for describing asymmetric carrieraggregation applied to individual terminals and control sequencethereof;

FIG. 4 is a diagram for describing ARQ control when carrier aggregationis applied to a terminal;

FIGS. 5A to 5D are diagrams for describing a method of transmitting anSR and a response signal by a terminal when channel selection is appliedas a method of transmitting a response signal, upon carrier performingaggregation communication using a plurality of downlink unit bands;

FIG. 6 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 7 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIGS. 8A to 8D are diagrams for describing a method of transmitting anSR and a response signal by a terminal according to Embodiment 1 of thepresent invention (when two downlink unit bands are set to a terminal);

FIGS. 9A and 9B are diagrams for describing mapping of a response signalin an ACK/NACK resource and an SR resource according to Embodiment 1 ofthe present invention (when two downlink unit bands are set to aterminal);

FIGS. 10A to 10D are diagrams for describing a method of transmitting anSR and a response signal by a terminal according to Embodiment 1 of thepresent invention (when three downlink unit bands are set to aterminal);

FIGS. 11A and 11B are diagrams for describing mapping of a responsesignal in an ACK/NACK resource and an SR resource according toEmbodiment 1 of the present invention (when three downlink unit bandsare set to a terminal);

FIGS. 12A to 12D are diagrams for describing a method of transmitting anSR and a response signal by a terminal according to Embodiment 2 of thepresent invention;

FIGS. 13A and 13B are diagrams for describing mapping of a responsesignal in an ACK/NACK resource and an SR resource according toEmbodiment 2 of the present invention (mapping example 1);

FIGS. 14A and 14B are diagrams for describing mapping of a responsesignal in an ACK/NACK resource and an SR resource according toEmbodiment 2 of the present invention (mapping example 2);

FIGS. 15A and 15B are diagrams for describing mapping of a responsesignal in an ACK/NACK resource and an SR resource according toEmbodiment 2 of the present invention (mapping example 3);

FIGS. 16A and 16B are diagrams for describing mapping of a responsesignal in an ACK/NACK resource and an SR resource according toEmbodiment 2 of the present invention (mapping example 4); and

FIGS. 17A and 17B are diagrams illustrating a variation of the presentinvention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In the followingembodiments, like reference numerals denote like parts, and theredundant description will not be repeated.

Embodiment 1

[Overview of Communication System]

In a communication system including base station 100 and terminal 200which will be described later, communication using uplink unit bands anda plurality of downlink unit bands associated with the uplink unit bandsis performed, that is, communication based on asymmetric carrieraggregation specific to terminal 200 is performed. This communicationsystem also includes a terminal that does not have a function ofperforming communication based on carrier aggregation and performscommunication by one downlink unit band and one uplink unit bandassociated with the downlink unit band (that is, communication not basedon carrier aggregation), unlike terminal 200.

Thus, base station 100 is configured to support both communicationsbased on asymmetric carrier aggregation and communication not based oncarrier aggregation.

Communication not based on carrier aggregation may be performed betweenbase station 100 and terminal 200 according to resource assignment withrespect to terminal 200 by base station 100.

In this communication system, when communication not based on carrieraggregation is performed, the ARQ is performed as in the conventionalart, whereas when communication based on carrier aggregation isperformed, the channel selection is employed in the ARQ. That is, thiscommunication system is, for example, an LTE-A system, base station 100is, for example, an LTE-A base station, and terminal 200 is, forexample, an LTE-A terminal. The terminal having no function ofperforming communication based on carrier aggregation is, for example,an LTE terminal.

In the following, a description will be made under the premise of thefollowing. That is, asymmetric carrier aggregation specific to terminal200 is configured between base station 100 and terminal 200 in advance,and information of a downlink unit band and an uplink unit band used byterminal 200 is shared between base station 100 and terminal 200.

[Configuration of Base Station]

FIG. 6 is a block diagram illustrating a configuration of base station100 according to Embodiment 1 of the present invention. Referring toFIG. 6, base station 100 includes control section 101, controlinformation generating section 102, coding section 103, modulatingsection 104, coding section 105, data transmission control section 106,modulating section 107, mapping section 108, IFFT section 109, CP addingsection 110, radio transmitting section 111, radio receiving section112, CP removing section 113, PUCCH extracting section 114, despreadingsection 115, sequence control section 116, correlation processingsection 117, deciding section 118, and retransmission control signalgenerating section 119.

Control section 101 assigns a downlink resource for transmitting controlinformation (that is, a downlink control information assignmentresource) and a downlink resource for transmitting downlink data (thatis, a downlink data assignment resource) to resource assignment targetterminal 200. This resource assignment is performed in a downlink unitband included in a unit band group set to resource assignment targetterminal 200. The downlink control information assignment resource isselected from among resources corresponding to the downlink controlchannel (PDCCH) in each downlink unit band. Further, the downlink dataassignment resource is selected from among resources corresponding tothe downlink data channel (PDSCH) in each downlink unit band. Further,when a plurality of resource assignment target terminals 200 arepresent, control section 101 assign different resources to respectiveresource assignment target terminals 200.

The downlink control information assignment resources are equivalent tothe above-described L1/L2 CCHs. That is, each of the downlink controlinformation assignment resources is configured with one or more CCEs.Further, the CCEs included in the downlink unit band are associated withcomponent resources of the uplink control channel region (PUCCH region)in an uplink unit band in the unit band group in a one-to-onecorrespondence manner (that is, an index of each CCE is associated withan index of the PUCCH in a one-to-one correspondence manner). That is,each CCE in a downlink unit band n is associated with a componentresource of a PUCCH region n in an uplink unit band in a unit band groupin a one-to-one correspondence manner.

Control section 101 determines a coding rate used to transmit controlinformation to resource assignment target terminal 200. Since the amountof data of the control information differs according to this codingrate, control section 101 assigns downlink control informationassignment resources having a number of CCEs to which the controlinformation having this amount of data can be mapped.

Control section 101 outputs information related to the downlink dataassignment resource to control information generating section 102.Further, control section 101 outputs information related to a codingrate to coding section 103. Further, control section 101 decides acoding rate of transmission data (that is, downlink data) and outputsthe decided coding rate to coding section 105. Further, control section101 outputs information related to the downlink data assignment resourceand information related to the downlink control information assignmentresource, to mapping section 108. Here, control section 101 performscontrol such that downlink data and downlink control information for thedownlink data are mapped to the same downlink unit band.

Control information generating section 102 generates control informationincluding information related to the downlink data assignment resource,and outputs the generated control information to coding section 103.This control information is generated for each downlink unit band. Whena plurality of resource assignment target terminals 200 are present, aterminal ID of a destination terminal is included in the controlinformation so as to discriminate between resource assignment targetterminals 200. For example, the control information includes a CRC bitmasked with the terminal ID of the destination terminal. This controlinformation may be called “downlink assignment control information(control information carrying downlink assignment).”

Coding section 103 encodes the control information according to thecoding rate received from control section 101, and outputs the encodedcontrol information to modulating section 104.

Modulating section 104 modulates the encoded control information andoutputs the modulated signal to mapping section 108.

Coding section 105 receives transmission data (that is, downlink data)of each destination terminal 200 and the coding rate information fromcontrol section 101 as input, encodes the transmission data, and outputsthe encoded transmission data to data transmission control section 106.Here, when a plurality of downlink unit bands are assigned todestination terminal 200, each transmission data transmitted througheach downlink unit band is encoded, and the encoded transmission data isthen output to data transmission control section 106.

At the time of first time transmission, data transmission controlsection 106 retains the encoded transmission data and also outputs theencoded transmission data to modulating section 107. The encodedtransmission data is retained for each destination terminal 200.Further, transmission data to one destination terminal 200 is retainedfor each downlink unit band to transmit. Thus, not only retransmissioncontrol of all data to be transmitted to destination terminal 200 butalso retransmission control of each downlink unit band can be performed.

Further, upon receiving NACK or DTX for downlink data transmittedthrough a certain downlink unit band from retransmission control signalgenerating section 119, data transmission control section 106 outputsretention data corresponding to the downlink unit band to modulatingsection 107. Upon receiving ACK for downlink data transmitted in acertain downlink unit band from retransmission control signal generatingsection 119, data transmission control section 106 deletes retentiondata corresponding to the downlink unit band.

Modulating section 107 modulates the encoded transmission data receivedfrom data transmission control section 106, and outputs a modulatedsignal to mapping section 108.

Mapping section 108 maps the modulated signal of the control informationreceived from modulating section 104 to a resource represented by thedownlink control information assignment resource received from controlsection 101, and outputs a mapping result to IFFT section 109.

Further, mapping section 108 maps the modulated signal of thetransmission data received from modulating section 107 to a resourcerepresented by the downlink data assignment resource received fromcontrol section 101, and outputs a mapping result to IFFT section 109.

The control information and the transmission data mapped to a pluralityof sub carriers in a plurality of downlink unit bands by mapping section108 are transformed from frequency-domain signals into time-domainsignals by IFFT section 109, are transformed into OFDM signals with a CPadded by CP adding section 110, are subjected to a transmission processsuch as a digital to analog (D/A) conversion process, an amplificationprocess and an up-conversion process by radio transmitting section 111,and are transmitted to terminal 200 through an antenna.

Radio receiving section 112 receives a response signal or a referencesignal transmitted from terminal 200 through the antenna, and performs areception process, such as a down-conversion process and an analog todigital (A/D) conversion process, on the response signal or thereference signal.

CP removing section 113 removes a CP added to the response signal or thereference signal that has been subjected to the reception process.

PUCCH extracting section 114 extracts PUCCH regions (PUCCH regionsrespectively corresponding to PUCCH resources) corresponding to M SRresources and N ACK/NACK resources from the PUCCH signal included in thereceived signal, and sorts the extracted PUCCH signals into processingsystems corresponding to the respective resources. Terminal 200transmits uplink control information (that is, either or both of the SRand the response signal) using any one of the PUCCH resources.

Despreading section 115-x and correlation processing section 117-xprocess the PUCCH signal extracted from the PUCCH region correspondingto an x-th PUCCH resource (the SR resource or the ACK/NACK resource.Here, x=1 to (M+N)). Base station 100 is provided with processingsystems of despreading section 115 and correlation processing section117 corresponding to each PUCCH resource x (the SR resource or theACK/NACK resource. Here, x=1 to (M+N)) used by base station 100.

Specifically, despreading section 115 despreads a signal of a portioncorresponding to the response signal using a Walsh sequence whichterminal 200 uses for secondary spreading in each PUCCH resource (the SRresource or the ACK/NACK resource), and outputs the despread signal tocorrelation processing section 117. Further, despreading section 115despreads a signal of a portion corresponding to the reference signalusing a DFT sequence which terminal 200 uses for spreading of thereference signal in each PUCCH resource (the SR resource or the ACK/NACKresource), and outputs the despread signal to correlation processingsection 117.

Sequence control section 116 generates a ZAC sequence that may bepossibly used to spread the response signal and the reference signaltransmitted from terminal 200. Further, sequence control section 116specifies correlation windows that respectively correspond to (M+N)PUCCH resources (SR resources and ACK/NACK resources), based on PUCCHresource which may be possibly used by terminal 200. Then, sequencecontrol section 116 outputs information representing the specifiedcorrelation window and the generated ZAC sequences to correlationprocessing section 117.

Correlation processing section 117 calculates a correlation valuebetween the signal input from despreading section 115 and the ZACsequence that may be possibly used for primary spreading in terminal 200using the information representing the correlation window and the ZACsequences input from sequence control section 116, and outputs thecalculated correlation value to deciding section 118.

Deciding section 118 decides whether or not the SR and the responsesignal are being transmitted from terminal 200, based on the correlationvalue input from correlation processing section 117. That is, decidingsection 118 decides whether or not any of the (M+N) PUCCH resources (SRresources and ACK/NACK resources) is being used by terminal 200 orwhether or not none of the (M+N) PUCCH resources is being used byterminal 200.

For example, when it is decided that any one of the M SR resources isbeing used by terminal 200 at timing when the terminal 200 transmits theresponse signal in response to the downlink data, deciding section 118decides that both the SR and the response signal are being transmittedfrom terminal 200. Further, when it is decided that any one of the M SRresources (or a predetermined one SR resource) is being used by terminal200 at timing other than timing when the terminal 200 transmits theresponse signal in response to the downlink data, deciding section 118decides that only the SR is being transmitted from terminal 200.Further, when it is decided that any of the N ACK/NACK resources isbeing used by terminal 200, deciding section 118 decides that only theresponse signal is being transmitted from terminal 200. Further, when itis decided that none of the resources is being used by the terminal,deciding section 118 decides that neither the SR nor the response signalis being transmitted from terminal 200.

In addition, when it is decided that terminal 200 is transmitting theSR, deciding section 118 outputs information related to the SR to anuplink resource assignment control section (not illustrated). Further,when it is decided that terminal 200 is transmitting the responsesignal, deciding section 118 decides a phase point represented by theresponse signal through synchronization detection. In detail, decidingsection 118 first determines a PUCCH resource from which a maximumcorrelation value has been detected among PUCCH resources correspondingto correlation processing sections 117-1 to 117-(M+N). Next, decidingsection 118 specifies a phase point of the response signal transmittedthrough the PUCCH resource from which the maximum correlation value hasbeen detected, and specifies a reception status pattern that correspondsto the PUCCH resource, the specified phase point, and the number ofdownlink unit bands through which its own station has transmitteddownlink data to terminal 200. Then, deciding section 118 individuallygenerates an ACK signal or a NACK signal on data transmitted in eachdownlink unit band based on the specified reception status pattern, andoutputs the ACK signal or the NACK signal to retransmission controlsignal generating section 119. Here, when all of correlation valuesobtained corresponding to the respective PUCCH resources are equal to orsmaller than a specific threshold value, deciding section 118 decidesthat non response signal has been transmitted from terminal 200,generates DTX for all downlink data, and outputs the DTX toretransmission control signal generating section 119.

Further, when the uplink resource assignment control section (notillustrated) receives the SR, base station 100 transmits the uplinkassignment control information (which may be also referred to as “uplinkgrant”) that notifies an uplink data assignment resource, to terminal200 so that terminal 200 can transmit uplink data. Thus, base station100 decides whether or not a resource for uplink data needs to beassigned to terminal 200, based on the uplink control channel. Thedetails of an operation in the uplink resource assignment controlsection and the details of an operation of base station 100 of assigninga resource for uplink data to terminal 200 will not be described.

Retransmission control signal generating section 119 generates aretransmission control signal for data (downlink data) transmitted ateach downlink unit band based on the information input from decidingsection 118. Specifically, when the response signal representing NACK orthe DTX is received, retransmission control signal generating section119 generates retransmission control signal representing aretransmission command, and outputs the retransmission control signal todata transmission control section 106. Further, when the response signalrepresenting ACK is received, retransmission control signal generatingsection 119 generates a retransmission control signal representing thatretransmission is not necessary, and outputs the retransmission controlsignal to data transmission control section 106.

[Configuration of Terminal]

FIG. 7 is a block diagram illustrating a configuration of terminal 200according to Embodiment 1 of the present invention. Referring to FIG. 7,terminal 200 includes radio receiving section 201, CP removing section202, fast Fourier transform (FFT) section 203, extracting section 204,demodulating section 205, decoding section 206, deciding section 207,control section 208, demodulating section 209, decoding section 210, CRCsection 211, response signal generating section 212, modulating section213, primary spreading section 214, secondary spreading section 215,IFFT section 216, CP adding section 217, and radio transmitting section218.

Radio receiving section 201 receives an OFDM signal transmitted frombase station 100 through an antenna, and performs a reception process,such as a down-conversion process, an A/D conversion process, on thereceived OFDM signal.

CP removing section 202 removes a CP added to the OFDM signal after thereception processing.

FFT section 203 transforms the received OFDM signal into a frequencydomain signal by FFT and outputs the received signal to extractingsection 204.

Further, extracting section 204 extracts the downlink control channelsignal (the PDCCH signal) from the received signal received from FFTsection 203 according to input coding rate information. That is, sincethe number of CCEs configuring the downlink control informationassignment resource changes depending on the coding rate, extractingsection 204 extracts the downlink control channel signal using thenumber of CCEs which corresponds to the coding rate as an extractionunit. Furthermore, the downlink control channel signal is extracted foreach downlink unit band. The extracted downlink control channel signalis output to demodulating section 205.

Further, extracting section 204 extracts downlink data from the receivedsignal based on the information related to the downlink data assignmentresource, which is addressed to its own terminal, received from decidingsection 207, and outputs the extracted downlink data to demodulatingsection 209.

Demodulating section 205 demodulates the downlink control channel signalreceived from extracting section 204, and outputs the obtaineddemodulation result to decoding section 206.

Decoding section 206 decodes the demodulation result received fromdemodulating section 205 according to the input coding rate information,and outputs the obtained decoding result to deciding section 207.

Deciding section 207 makes a blind decision as to whether or not controlinformation included in the decoding result received from decodingsection 206 is control information addressed to its own terminal. Thisdecision is made using the decoding result corresponding to theextraction unit as a unit. For example, deciding section 207 demasks aCRC bit using the terminal ID of its own terminal, and decides controlinformation with CRC=OK (no error) as the control information addressedto its own terminal. Then, deciding section 207 outputs informationrelated to the downlink data assignment resource for its own terminal,which is included in the control information addressed to its ownterminal, to extracting section 204.

Further, deciding section 207 specifies each CCE to which the controlinformation addressed to its own terminal is mapped in the downlinkcontrol channel of each downlink unit band, and outputs anidentification number (that is, CCE index) of the specified CCE tocontrol section 208.

Control section 208 specifies a PUCCH resource (frequency/code)corresponding to the CCE to which the downlink control informationreceived at an n-th (n=first to N-th) unit band is mapped, that is, aPUCCH resource n (That is, an ACK/NACK resource n) in a PUCCH region n,based on the CCE identification number received from deciding section207. Then, control section 208 decides a PUCCH resource to be used totransmit the response signal, among the specified N ACK/NACK resourcesand the M SR resources previously notified from base station 100.

Specifically, control section 208 decides a PUCCH resource to be usedand a phase point to be set so as to transmit a signal according to atransmission rule (a mapping rule) of the response signal, which will bedescribed later, based on the generation status information of the SRreceived from an uplink data generating section (not illustrated) and anerror detection result (that is, a reception success/failure pattern) ofdownlink data at each downlink unit band received from CRC section 211.

Then, control section 208 outputs information related to the phase pointto be set, to response signal generating section 212, outputs the ZACsequence and the cyclic shift index corresponding to the PUCCH resourcesto be used to primary spreading section 214 and outputs frequencyresource information to IFFT section 216. Here, when there is noresponse signal to be transmitted through the sub frame having receivedthe SR from the uplink data generating section (that is, when thedownlink assignment control information is not detected at all), controlsection 208 instructs response signal generating section 212 to output“NACK” to modulating section 213. Further, control section 208 outputs aWalsh sequence and a DFT sequence corresponding to the PUCCH resourcesto be used to secondary spreading section 215. The details of control onthe PUCCH resource and the phase points by control section 208 will bedescribed later.

Demodulating section 209 demodulates the downlink data received fromextracting section 204, and outputs the demodulated downlink data todecoding section 210.

Decoding section 210 decodes the downlink data received fromdemodulating section 209, and outputs the decoded downlink data to CRCsection 211.

CRC section 211 generates the decoded downlink data received fromdecoding section 210, and performs error detection for each downlinkunit band using a CRC. Then, CRC section 211 outputs ACK to controlsection 208 when CRC=OK (no error), but outputs NACK to control section208 when CRC=NG (error). Further, when CRC=OK (no error), CRC section211 outputs the decoded downlink data as received data.

Response signal generating section 212 generates the response signal andthe reference signal based on the phase point of the response signalinstructed from control section 208, and outputs the response signal andthe reference signal to modulating section 213.

Modulating section 213 modulates the response signal and the referencesignal input from response signal generating section 212, and outputsthe modulated response signal and the modulated reference signal toprimary spreading section 214.

Primary spreading section 214 performs primary-spreading on the responsesignal and the reference signal based on the ZAC sequence and the cyclicshift index set by control section 208, and outputs the primary-spreadresponse signal and the primary-spread reference signal to secondaryspreading section 215. That is, primary spreading section 214 performsprimary-spreading on the response signal and the reference signalaccording to an instruction from control section 208. Here, “spreading”specifically means multiplying the response signal represented byinformation of one symbol by the ZAC sequence.

Secondary spreading section 215 performs secondary-spreading on theresponse signal and the reference signal using a Walsh sequence and aDFT sequence set by control section 208, and outputs thesecondary-spread signal to IFFT section 216. That is,secondary-spreading section 215 performs secondary-spreading on theprimary-spread response signal and the primary-spread reference signalusing the Walsh sequence and the DFT sequence corresponding to the PUCCHresources selected by control section 208, and outputs the spread signalto IFFT section 216. That is, secondary spreading section 215 multipliesthe response signal and the reference signal which have been subjectedto primary spreading by a component of the Walsh sequence or a componentof the DFT sequence.

CP adding section 217 adds the same signal as the tail part of thesignal which has been subjected to IFFT, to the head of the signal as aCP.

Radio transmitting section 218 performs transmission processing, such asa D/A conversion process, an amplification process, and an up-conversionprocess, on the input signal. Then, radio transmitting section 218transmits the signal to base station 100 through the antenna.

[Operation of Terminal 200]

An operation of terminal 200 having the above configuration will bedescribed.

<Reception of Downlink Assignment Control Information and Downlink Databy Terminal 200>

Terminal 200 makes a blind decision as to whether or not downlinkassignment control information addressed to its own terminal has beentransmitted for each sub frame in all downlink unit bands of a unit bandgroup set to its own terminal.

Specifically, deciding section 207 decides whether or not the downlinkassignment control information addressed to its own terminal is includedin the downlink control channel of each downlink unit band. Then, whenit is decided that the downlink assignment control information addressedto its own terminal is included, deciding section 207 outputs thedownlink assignment control information to extracting section 204.Further, deciding section 207 outputs the identification information ofthe downlink unit band in which the downlink assignment controlinformation addressed to its own terminal has been detected, to controlsection 208. Thus, control section 208 is notified of the downlink unitband in which the downlink assignment control information addressed toits own terminal has been detected.

Extracting section 204 extracts downlink data from the received signalbased on the downlink assignment control information received fromdeciding section 207. Extracting section 204 extracts the downlink datafrom the received signal based on the resource information included inthe downlink assignment control information.

For example, downlink assignment control information transmitted atdownlink unit band 1 includes information related to a resource used fortransmission of downlink data (DL data) transmitted at downlink unitband 1, and downlink assignment control information transmitted atdownlink unit band 2 includes information related to a resource used fortransmission of downlink data transmitted at downlink unit band 2.

Thus, terminal 200 can receive downlink data at both downlink unit band1 and downlink unit band 2 by receiving the downlink assignment controlinformation transmitted at downlink unit band 1 and the downlinkassignment control information transmitted at downlink unit band 2. Onthe other hand, when the terminal is difficult to receive the downlinkassignment control information at a certain downlink unit band, terminal200 is difficult to receive downlink data at the corresponding downlinkunit band.

<Transmission of Response and SR by Terminal 200>

CRC section 211 performs error detection on downlink data correspondingto the successfully received downlink assignment control information,and outputs an error detection result to control section 208.

Then, control section 208 performs transmission control of the responsesignal as follows, based on the generation status of the SR receivedfrom the uplink data generating section (not illustrated) and the errordetection result received from CRC section 211. FIGS. 8 and 9 arediagrams for describing a method of transmitting an SR and a responsesignal through terminal 200 when two downlink unit bands are set toterminal 200. FIGS. 10 and 11 are diagrams for describing a method oftransmitting an SR and a response signal through terminal 200 when threedownlink unit bands are set to terminal 200.

<Transmission of Response and SR by Terminal 200: When There are TwoDownlink Unit Bands>

A description will be made below in connection with an example in whichtwo downlink unit bands (downlink unit bands 1 and 2) are set toterminal 200. Here, an ACK/NACK resource (PUCCH resource) associatedwith a downlink control information assignment resource used fordownlink assignment control information for downlink data transmitted indownlink unit band 1 is defined as ACK/NACK resource 1. Further, anACK/NACK resource (PUCCH resource) associated with a downlink controlinformation assignment resource used for downlink assignment controlinformation for downlink data transmitted in downlink unit band 2 isdefined as ACK/NACK resource 2.

Further, in the following description, base station 100 independentlynotifies terminal 200 of information related to a resource (an SRresource illustrated in FIG. 8A) for transmitting an SR in an uplinkunit band illustrated in FIG. 4 (an uplink unit band set to terminal200). That is, control section 208 of terminal 200 retains informationrelated to an SR resource notified from base station 100 through aseparate signaling unit (for example, higher layer signaling).

Further, terminal 200 specifies an ACK/NACK resource associated with aCCE, which is occupied by downlink assignment control informationreceived by its own terminal, among a plurality of CCEs configuringPDCCHs of downlink unit bands 1 and 2, as ACK/NACK resource 1 or 2.

Here, in FIG. 8A, an SR resource and ACK/NACK resources 1 and 2 aredifferent code resources from each other that at least one of a ZACsequence (primary spreading) or a Walsh sequence/DFT sequence isdifferent.

An operation of terminal 200 at this time is described in detail withreference to FIGS. 9A and 9B. Here, ACK/NACK resources 1 and 2illustrated in FIG. 9A and an SR resource illustrated in FIG. 9Bcorrespond to ACK/NACK resources 1 and 2 and an SR resource illustratedin FIGS. 8A to 8D, respectively. Further, in FIGS. 9A and 9B, “A”represents ACK, “N” represents NACK, and “D” represents DTX. In FIGS. 9Aand 9B, for example, “A/N” represents a state in which a response signalcorresponding to downlink unit band 1 (CC1) is ACK but a response signalcorresponding to downlink unit band 2 (CC2) is NACK. Further, “N/D”represents a state in which a response signal corresponding to downlinkunit band 1 (CC1) is NACK and it was difficult to detect downlinkassignment control information corresponding to downlink datatransmitted in downlink unit band 2 (CC2) (that is, DTX corresponding todownlink unit band 2 (CC2)). Further, in FIG. 9B, for example, “SR+A/N”represents a state in which “A/N” is transmitted using an SR resource.At this time, base station 100 detects an SR from terminal 200 sidebased on whether or not the SR resource is being used, and determinesthat a response signal is “A/N” based on a phase point to which thesignal is mapped.

First, when terminal 200 transmits only the response signal (“when onlyresponse signal is transmitted” illustrated in FIG. 8B), terminal 200performs an operation of the channel selection using ACK/NACK resources1 and 2 associated with CCEs occupied by downlink assignment controlinformation corresponding to downlink data transmitted in downlink unitbands 1 and 2 as illustrated in FIG. 9A. Specifically, control section208 of terminal 200 transmits the response signal using a transmissionrule (a mapping rule) of the response signal illustrated in FIG. 9A,based on a pattern (state) as to whether or not downlink data addressedto its own terminal, which correspond to downlink assignment controlinformation and have been transmitted in downlink unit bands 1 and 2,have been successfully received (error detection result).

Here, it should be noted that states (D/A and D/N) in which DTX has beengenerated for downlink unit band 1 (CC1) are all notified by the phasepoint of ACK/NACK resource 2 other than ACK/NACK resource 1 illustratedin FIG. 9A. This is because when terminal 200 did not detect downlinkassignment control information corresponding to downlink data indownlink unit band 1 (that is, in case of DTX), it is difficult tospecify ACK/NACK resource 1 to be used at terminal 200 side. Similarly,states (A/D and N/D) in which DTX has been generated on downlink unitband 2 (CC2) are all notified by the phase point of ACK/NACK resource 1,not by ACK/NACK resource 2 illustrated in FIG. 9A. This is because whenterminal 200 did not detect downlink assignment control informationcorresponding to downlink data in downlink unit band 2 (that is, in caseof DTX), it is difficult to specify ACK/NACK resource 2 to be used atterminal 200 side. As described above, in the ACK/NACK resource, thereis a limitation to a resource which can be used to notify a state inwhich DTX has been generated.

In FIG. 9A, if all of three states (N/D, D/N, and N/N) in which all isNACK or DTX can be notified through the same resource and at the samephase point, a total of four phase points become necessary to notify allstates (8 states illustrated in FIG. 9A (a total of 8 receptionsuccess/failure patterns). That is, any one of the two ACK/NACKresources illustrated in FIG. 9A may be reduced. However, due to thelimitation of the ACK/NACK resource, when terminal 200 transmits onlythe response signal as illustrated in FIG. 8B, two ACK/NACK resources 1and 2 (that is, resources the number of which is equal to the number ofdownlink unit bands set to terminal 200) become necessary.

On the other hand, when terminal 200 simultaneously transmits the SR andthe response signal in the same sub frame (“when SR and response signalare transmitted” illustrated in FIG. 8C), terminal 200 transmits theresponse signal using the SR resource notified from base station 100 bya separate signaling technique as illustrated in FIG. 9B. Specifically,control section 208 of terminal 200 transmits the response signal usingthe transmission rule (the mapping rule) of the response signalillustrated in FIG. 9B based on the pattern (state) as to whether or notdownlink data corresponding to downlink assignment control informationaddressed to its own terminal has been successfully received (errordetection result).

Here, a description will be made in connection with the transmissionrule (mapping rule) (FIG. 9B) of the response signal used when the SRand the response signal have been simultaneously generated in the samesub frame (“when SR and response signal are transmitted” illustrated inFIG. 8C).

In FIG. 9B, when all of two pieces of downlink assignment controlinformation and downlink data transmitted in downlink unit bands 1 and 2corresponding to the respective downlink assignment control informationhave been successfully received, a phase point (−1, 0) is used. That is,in FIG. 9B, “A/A” is associated with the phase point (−1, 0) of the SRresource.

Further, when, of downlink data of downlink unit bands 1 and 2corresponding to the two pieces of downlink assignment controlinformation, downlink data of downlink unit band 1 has been successfullyreceived but downlink data of downlink unit band 2 has been failed inreception, a phase point of (0, −j) is used. That is, in FIG. 9B, “A/N”and “A/D” are associated with the phase point (0, −j) of the SRresource.

Further, when, of downlink data of downlink unit bands 1 and 2corresponding to the two pieces of downlink assignment controlinformation, downlink data of downlink unit band 1 has been failed inreception but downlink data of downlink unit band 2 has beensuccessfully received, a phase point of (0, j) is used. That is, in FIG.9B, “N/A” and “D/A” are associated with the phase point (0, j) of the SRresource.

Further, when none of downlink data of downlink unit bands 1 and 2corresponding to the two pieces of downlink assignment controlinformation have been received, a phase point of (1, 0) is used. Thatis, in FIG. 9B, “N/N”, “D/N”, and “N/D” are associated with the phasepoint (1, 0) of the SR resource.

That is, in the transmission rule (mapping rule) illustrated in FIG. 9B(when the SR and the response signal have been simultaneously generatedin the same sub frame), a reception success/failure (error detectionresult) pattern candidate is associated with the phase point of theresponse signal in the SR resource, and different phase points in the SRresource are associated with pattern candidate groups which differ in atleast one of the number of ACKs included in the pattern and the positionof ACK (that is, the downlink unit band to which successfully receiveddownlink data is assigned) in the pattern. That is, in FIG. 9B, thereception success/failure (error detection result) pattern candidate isassociated with the phase point of the response signal in the SRresource, different phase points in the SR resource are associated withpattern candidate groups which differ in the number of ACKs included inthe pattern, and different phase points in the SR resource areassociated with pattern candidate groups which are equal in the numberof ACKs included in the pattern but differ in the position of ACK (thatis, the downlink unit band to which successfully received downlink datais assigned) in the pattern. Thus, even in the case in which alldownlink data corresponding to the detected downlink assignment controlinformation have been successfully received, when the number ofsuccessfully received downlink data (the number of ACKs) is different orwhen the downlink unit band to which successfully received downlink datahas been assigned (the position of ACK) is different even though thenumber of successfully received downlink data (the number of ACKs) isthe same, different phase points in the SR resource are used for theresponse signal.

For example, in FIG. 9B, when downlink data has been successfullyreceived in all of downlink unit bands (“A/A”), the phase point (−1, 0)is used. Further, when downlink data has been successfully received indownlink unit band 1 but downlink data has failed in reception indownlink unit band 2 (“A/N” and “A/D”), the phase point (0, −j) is used.Further, when downlink data has failed in reception in downlink unitband 1 but downlink data has been successfully received in downlink unitband 2 (“N/A” and “D/A”), the phase point (0, j) is used. Further, whendownlink data has not been received in all of downlink unit bands(“N/N”, “D/N”, and “N/D”), the phase point (−1, 0) is used.

Here, the SR resource illustrated in FIG. 9B is notified by a separatesignaling technique (for example, higher layer signaling) from basestation 100 to terminal 200. Thus, in FIG. 9B (“when SR and responsesignal are transmitted” illustrated in FIG. 8C), there is no limitationas in FIG. 9A (“when only response signal is transmitted” illustrated inFIG. 8B), and all of the three states “N/D”, “D/N”, and “N/N” can beassociated with the same resource and the same phase point (here, thephase point (1, 0)). Thus, in FIG. 9B, a total of 4 phase points arenecessary for notifying all states (a total of 8 states illustrated inFIG. 9B (8 reception success/failure patterns)).

That is, in FIG. 9A, due to the limitation, a total of 5 phase pointsare necessary for notifying all states (reception success/failurepatterns), and two ACK/NACK resources are necessary for notifying theresponse signals of downlink unit bands 1 and 2. On the other hand, inFIG. 9B, a single SR resource (PUCCH resource) may be used tosimultaneously notify the SR and the response signals of downlink unitbands 1 and 2.

As described above, when terminal 200 simultaneously transmits the SRand the response signal, mapping illustrated in FIG. 9B is used. Thus,even when the channel selection is applied as a method of transmittingthe response signal, the number of SR resources can be reduced. Forexample, when FIG. 5A is compared with FIG. 8A, four PUCCH resources (SRresources and ACK/NACK resources) are necessary in FIG. 5A, whereasthree PUCCH resources (SR resources and ACK/NACK resources) arenecessary in FIG. 8A. That is, in FIG. 8A, one PUCCH resource is deletedcompared to FIG. 5A, thus an increase in the overhead of the uplinkcontrol channel (PUCCH) can be suppressed.

In FIG. 9B, it should be noted that a case (“A/A” illustrated in FIG.9B) in which all response signals to downlink unit bands 1 and 2 atterminal 200 side are ACK and cases (“N/N”, “D/N”, and “N/D” illustratedin FIG. 9B) in which all response signals to downlink unit bands 1 and 2at terminal 200 side are NACK or DTX are associated with phase pointsfarthest from each other, among phase points (4 phase points) which canbe selected by the reception success/failure (error detection result)pattern candidate group.

That is, in FIG. 9B, the states (the reception success/failure patterncandidate group) of the response signals notified using adjacent phasepoints (that is, phase points having a phase difference of 90° (π/2radians)) in the SR resource are different from each other only in thereception status in one downlink unit band. For example, in the SRresource illustrated in FIG. 9B, the state “A/A” notified using thephase point (−1, 0) and the states “N/A” and “D/A” notified using thephase point (0, j) (having a phase difference of 90° with the phasepoint (−1, 0)) are different from each other only in the receptionstatus of downlink unit band 1 (CC1). Similarly, in the SR resourceillustrated in FIG. 9B, the state “A/A” notified using the phase point(−1, 0) and the states “A/N” and “A/D” notified using the phase point(0, −j) (having a phase difference of 90° with the phase point (−1, 0))are different from each other only in the reception status of downlinkunit band 2 (CC2). This is similarly applied to the other phase points.

As a result, even when the phase point is erroneously decided, basestation 100 side (deciding section 118) can suppress the number of unitbands erroneous in a retransmission control to a minimum, therebyminimizing degradation in retransmission efficiency.

Further, when terminal 200 transmits only the SR (“when only SR istransmitted” illustrated in FIG. 8D), terminal 200 transmits the SRusing the SR resource separately notified from base station 100 asillustrated in FIG. 9B. At this time, control section 208 of terminal200 transmits the SR using the same phase point (1, 0) as the state (thereception success/failure pattern) in which all is NACK (or DTX), whichis illustrated in FIG. 9B.

<Transmission of Response and SR by Terminal 200: When There are ThreeDownlink Unit Bands>

The following description will be made in connection with an example inwhich three downlink unit bands (downlink unit bands 1, 2, and 3) areset to terminal 200. Here, an ACK/NACK resource (PUCCH resource)associated with a downlink control information assignment resource usedfor downlink assignment control information for downlink datatransmitted in downlink unit band 1 is defined as ACK/NACK resource 1.Further, an ACK/NACK resource (PUCCH resource) associated with adownlink control information assignment resource used for downlinkassignment control information for downlink data transmitted at downlinkunit band 2 is defined as ACK/NACK resource 2. Further, an ACK/NACKresource (PUCCH resource) associated with a downlink control informationassignment resource used for downlink assignment control information fordownlink data transmitted at downlink unit band 3 is defined as ACK/NACKresource 3.

Further, in the following description, base station 100 separatelynotifies terminal 200 of information related to two resources (SRresources 1 and 2 illustrated in FIG. 10A) for transmitting an SR in anuplink unit band illustrated in FIG. 4 (an uplink unit band set toterminal 200). That is, control section 208 of terminal 200 retainsinformation related to SR resources 1 and 2 notified from base station100.

Further, terminal 200 specifies an ACK/NACK resource associated with aCCE, which is occupied by downlink assignment control informationreceived by its own terminal, among a plurality of CCEs configuringPDCCHs of downlink unit bands 1, 2, and 3 as ACK/NACK resource 1, 2, or3.

Here, in FIG. 10A, SR resources 1 and 2 and ACK/NACK resources 1, 2, and3 are different code resources from each other such that at least one ofa ZAC sequence (primary spreading) or a Walsh sequence/DFT sequence isdifferent.

An operation of terminal 200 at this time is described in detail withreference to FIGS. 11A and 11B. Here, ACK/NACK resources 1, 2, and 3illustrated in FIG. 11A and SR resources 1 and 2 illustrated in FIG. 11Bcorrespond to ACK/NACK resources 1, 2, and 3 and SR resources 1 and 2illustrated in FIGS. 10A to 10D, respectively. In FIGS. 11A and 11B, forexample, “A/N/N” represents a state in which a response signalcorresponding to downlink unit band 1 (CC1) is ACK but response signalscorresponding to downlink unit band 2 (CC2) and downlink unit band 3(CC3) are NACK. Further, “N/D/D” represents a state in which a responsesignal corresponding to downlink unit band 1 (CC1) is NACK and it wasdifficult to detect downlink assignment control informationcorresponding to downlink data transmitted in downlink unit band 2 (CC2)and downlink unit band 3 (CC3) (that is, DTXs corresponding to downlinkunit band 2 (CC2) and downlink unit band 3 (CC3)). Further, in FIG. 11B,for example, “SR+A/N/N” represents a state in which “A/N/N” istransmitted using an SR resource.

First, when terminal 200 transmits only the response signal (“when onlyresponse signal is transmitted” illustrated in FIG. 10B), terminal 200performs an operation of the channel selection using ACK/NACK resources1, 2, and 3 associated with CCEs occupied by downlink assignment controlinformation corresponding to downlink data transmitted in downlink unitbands 1, 2, and 3 as illustrated in FIG. 11A. Specifically, controlsection 208 of terminal 200 transmits the response signal using atransmission rule (a mapping rule) of the response signal illustrated inFIG. 11A based on a pattern (state) as to whether or not downlink dataassociated with downlink assignment control information corresponding todownlink data addressed to its own terminal, which have been transmittedin downlink unit bands 1, 2, and 3, have been successfully received(error detection result).

Here, it should be noted that states (D/D/A and D/D/N) in which DTXshave been generated for downlink unit band 1 (CC1) and downlink unitband 2 (CC2) are all notified by the phase point of ACK/NACK resource 3,not by ACK/NACK resources 1 and 2 illustrated in FIG. 11A. This isbecause when terminal 200 did not detect downlink assignment controlinformation corresponding to downlink data transmitted in downlink unitbands 1 and 2 (that is, in case of DTX), it is difficult to specifyACK/NACK resources 1 and 2 to be used at terminal 200 side. Similarly,states (A/D/D and N/D/D) in which DTXs have been generated for downlinkunit band 2 (CC2) and downlink unit band 3 (CC3) are all notified by thephase point of ACK/NACK resource 1. States (D/A/D and D/N/D) in whichDTXs have been generated for downlink unit band 1 (CC1) and downlinkunit band 3 (CC3) are all notified by the phase point of ACK/NACKresource 2. Further, a state in which DTX has been generated fordownlink unit band 1 is notified by phase points of ACK/NACK resources 2and 3 other than ACK/NACK resource 1 illustrated in FIG. 11A. It issimilarly applied to a state in which DTX has been generated fordownlink unit bands 2 and 3. As described above, in the ACK/NACKresource, there is a limitation to a resource which can be used tonotify a state in which DTX has been generated.

In FIG. 11A, if all of seven states (“N/N/N”, “N/N/D”, “N/D/N”, “N/D/D”,“D/N/N”, and “D/N/D”) in which all is NACK or DTX can be notifiedthrough the same resource and at the same phase point, a total of 8phase points are necessary to notify all states (a total of 26 statesillustrated in FIG. 11A (26 reception success/failure patterns)). Thatis, it is possible to reduce any one of the three ACK/NACK resourcesillustrated in FIG. 11A. However, due to the limitation of the ACK/NACKresource, when terminal 200 transmits only the response signal asillustrated in FIG. 10B, three ACK/NACK resources 1, 2, and 3 (that is,resources of which the number is equal to that of downlink unit bandsset to terminal 200) are necessary.

On the other hand, when terminal 200 simultaneously transmits the SR andthe response signal in the same sub frame (“when SR and response signalare transmitted” illustrated in FIG. 10C), terminal 200 transmits theresponse signal using the SR resource separately notified from basestation 100 as illustrated in FIG. 11B. Specifically, control section208 of terminal 200 transmits the response signal using the transmissionrule (the mapping rule) of the response signal illustrated in FIG. 11B,based on the pattern (state) as to whether or not downlink datacorresponding to downlink assignment control information addressed toits own terminal has been successfully received (error detectionresult).

Here, a description will be made in connection with the transmissionrule (mapping rule) (FIG. 11B) of the response signal used when the SRand the response signal have been simultaneously generated in the samesub frame (“when SR and response signal are transmitted” illustrated inFIG. 10C).

In the transmission rule (mapping rule) illustrated in FIG. 11B (whenthe SR and the response signal have been simultaneously generated in thesame sub frame), a reception success/failure (error detection result)pattern candidate is associated with the SR resource to which theresponse signal is assigned and the phase point of the response signal,and SR resources and phase points which differ in at least one of the SRresource and the phase point are associated with pattern candidategroups which differ in at least one of the number of ACKs included inthe pattern and the position of ACK (that is, the downlink unit band towhich successfully received downlink data is assigned) in the pattern.That is, in FIG. 11B, the reception success/failure (error detectionresult) pattern candidate is associated with a pair of the SR resourceand the phase point of the response signal, different pairs (pairs ofthe SR resources and the phase points) are associated with patterncandidate groups which differ in the number of ACKs included in thepattern, and different pairs (pairs of the SR resources and the phasepoints) are associated with pattern candidate groups which are equal inthe number of ACKs included in the pattern but differ in the position ofACK (that is, the downlink unit band to which successfully receiveddownlink data is assigned) in the pattern. Thus, even in the case inwhich all downlink data corresponding to the detected downlinkassignment control information have been successfully received, when thenumber of successfully received downlink data (the number of ACKs) isdifferent or when the downlink unit band to which successfully receiveddownlink data has been assigned (the position of ACK) is different eventhough the number of successfully received downlink data (the number ofACKs) is the same, different SR resources and different phase points areused for the response signal.

For example, in FIG. 11B, when downlink data has been successfullyreceived in all of downlink unit bands (“A/A/A”), the phase point (−1,0) of SR resource 2 is used. Further, when downlink data has beensuccessfully received in downlink unit bands 1 and 2 but downlink datahas not been received in downlink unit band 3 (“A/A/N” and “A/A/D”), thephase point (−1, 0) of SR resource 1 is used. Further, when downlinkdata has been successfully received in downlink unit bands 1 and 3 butdownlink data has not been successfully received in downlink unit band 2(“A/N/A” and “A/D/A”), the phase point (0, j) of SR resource 2 is used.Further, when downlink data has been successfully received in downlinkunit band 1 but downlink data has not been received in downlink unitbands 2 and 3 (“A/N/N”, “A/N/D”, “A/D/N”, and “A/D/D”), the phase point(0, j) of SR resource 1 is used. Further, when downlink data has notbeen received in downlink unit band 1 but downlink data has beensuccessfully received in downlink unit bands 2 and 3 (“N/A/A” and“D/A/A”), the phase point (0, −j) of SR resource 2 is used. Further,when downlink data has not been received in downlink unit bands 1 and 3but downlink data has been successfully received in downlink unit band 2(“N/A/N”, “N/A/D”, “D/A/N”, and “D/A/D”), the phase point (0, −j) of SRresource 1 is used. Further, when downlink data has not been received indownlink unit bands 1 and 2 but downlink data has been successfullyreceived in downlink unit band 3 (“N/N/A”, “N/D/A”, “D/N/A”, and“D/D/A”), the phase point (1, 0) of SR resource 2 is used. Further, whendownlink data has not been received in all of downlink unit bands(“N/N/N”, “N/N/D”, “N/D/N”, “N/D/D”, “D/N/N”, “D/N/D”, and “D/D/N”), thephase point (1, 0) of SR resource 1 is used.

Here, the SR resource illustrated in FIG. 11B is notified from basestation 100 to terminal 200 in advance, similarly to FIG. 9B. Thus, inFIG. 11B (“when SR and response signal are transmitted” illustrated inFIG. 10C), there is no limitation as in FIG. 11A (“when only responsesignal is transmitted” illustrated in FIG. 10B), and all of the sevenstates (“N/N/N”, “N/N/D”, “N/D/N”, “N/D/D”, “D/N/N”, and “D/N/D”) can beassociated with the same resource and the same phase point (in FIG. 11B,the phase point (1, 0) of SR resource 1). Thus, in FIG. 11B, a total of8 phase points are necessary for notifying all states (a total of 26states illustrated in FIG. 11B (26 reception success/failure patterns)).

That is, in FIG. 11A, due to the limitation, a total of 10 phase pointsare necessary for notifying all states (reception success/failurepatterns), and three ACK/NACK resources are necessary for notifying theresponse signals of downlink unit bands 1, 2, and 3. On the other hand,in FIG. 11B, two SR resources (PUCCH resources) may be used to notifythe SR and the response signals of downlink unit bands 1, 2, and 3.

As described above, when terminal 200 simultaneously transmits the SRand the response signal, mapping illustrated in FIG. 11B is used. Thus,even when the channel selection is applied as a method of transmittingthe response signal, the number of SR resources can be suppressed. InFIG. 10A, two SR resources, which are less by one resource than threeACK/NACK resources, are preferably prepared. That is, in FIG. 10A, fivePUCCH resources (SR resources and ACK/NACK resources) are enough fortransmitting the SR and the response signal.

In FIG. 11B, it should be noted that the states (the receptionsuccess/failure pattern candidate group) of the response signalsnotified using adjacent phase points (that is, phase points having aphase difference of 90° (π/2 radians)) in the same resource aredifferent from each other only in the reception status in one downlinkunit band. For example, in SR resource 2 illustrated in FIG. 11B, thestate “A/A/A” notified using the phase point (−1, 0) and the states“A/N/A” and “A/D/A” notified using the phase point (0, j) (having aphase difference of 90° with respect to the phase point (−1, 0)) aredifferent from each other only in the reception status of downlink unitband 2 (CC2). Similarly, in SR resource 2 illustrated in FIG. 11B, thestate “A/A/A” notified using the phase point (−1, 0) and the states“N/A/A” and “D/A/A” notified using the phase point (0, −j) (having aphase difference of 90° with respect to the phase point (−1, 0)) aredifferent from each other only in the reception status of downlink unitband 1 (CC1). This is similarly applied to the other phase points.

As a result, similarly to FIG. 9B, even when the phase point iserroneously decided, base station 100 side (deciding section 118) cansuppress the number of unit bands having a retransmission control errorto a minimum, thereby minimizing degradation in retransmissionefficiency.

Further, when terminal 200 transmits only the SR (“when only SR istransmitted” illustrated in FIG. 10D), terminal 200 transmits the SRusing the same resource (SR resource 1) and the same phase point (1, 0)as in the state (reception success/failure pattern) in which all is NACK(or DTX), as illustrated in FIG. 11B.

As described above, according to the present embodiment, control section208 of terminal 200 performs transmission control of the SR and theresponse signal, based on the generation status of the SR and thepattern as to whether or not downlink data has been successfullyreceived in the downlink unit band included in the unit band group setto its own terminal (error detection result). Further, when the SR andthe response signal have been simultaneously generated in the same subframe, control section 208 causes a pair of the PUCCH resource (SRresource) for notifying the response signal and the phase point of theresponse signal to be different according to the number of successfullyreceived downlink data (that is, the number of ACKs) and the downlinkunit band (that is, the position of ACK in the reception success/failurepattern) to which successfully received downlink data has been assignedin each reception success/failure (error detection result) pattern. Thatis, a pair of the PUCCH resource (SR resource) and the phase point ofthe response signal selected by terminal 200 differs according to thenumber of successfully received downlink data (that is, the number ofACKs) and the downlink unit band (that is, the position of ACK in thereception success/failure pattern) to which successfully receiveddownlink data has been assigned in each reception success/failurepattern.

As a result, base station 100 which is a reception side of the responsesignal can specify a combination of downlink unit bands in whichdownlink data has been successfully received, based on the PUCCHresource through which the response signal has been received and thephase point of the response signal. Further, terminal 200 changes thePUCCH resource (the ACK/NACK resource or the SR resource) and thetransmission rule (mapping rule) according to the generation status ofthe SR at terminal 200 side. At this time, when the SR and the responsesignal have been simultaneously generated in the same sub frame,terminal 200 notifies the response signal using all phase points(constellation points) of the SR resource. Thus, the number of SRresources necessary for notifying the SR and the response signal can bereduced. That is, the number of SR resources to be notified from basestation 100 to terminal 200 can be reduced. As described above,according to the present embodiment, even when the channel selection isapplied as a method of transmitting the response signal in the LTE-A,the amount of an increase in the overhead of the uplink control channel(PUCCH) can be suppressed, and the SR and the response signal can besimultaneously transmitted.

Embodiment 2

In Embodiment 2, the terminal cancels transmission of ACK information insome of downlink unit bands so as to further reduce the overhead of theuplink control channel (PUCCH) compared to Embodiment 1. That is, theterminal drops ACK information in some downlink unit bands. Thus, inEmbodiment 2, the overhead of the uplink control channel (PUCCH) can befurther reduced compared to Embodiment 1.

A concrete description will be made below. Basic configurations of thebase station and the terminal according to Embodiment 2 are the same asin Embodiment 1, and thus a description will be made with reference toFIG. 6 (base station 100) and FIG. 7 (terminal 200).

[Operation of Terminal 200: When there are Three Downlink Unit Bands]

The following description will be made in connection with an example inwhich three downlink unit bands (downlink unit bands 1, 2, and 3) areset to terminal 200. Here, similarly to Embodiment 1, an ACK/NACKresource (PUCCH resource) associated with a downlink control informationassignment resource used for downlink assignment control information fordownlink data transmitted in downlink unit band 1 is defined as ACK/NACKresource 1. Further, an ACK/NACK resource (PUCCH resource) associatedwith a downlink control information assignment resource used fordownlink assignment control information for downlink data transmitted indownlink unit band 2 is defined as ACK/NACK resource 2. Further, anACK/NACK resource (PUCCH resource) associated with a downlink controlinformation assignment resource used for downlink assignment controlinformation for downlink data transmitted in downlink unit band 3 isdefined as ACK/NACK resource 3.

Further, in the following description, base station 100 notifiesterminal 200 of information related to one resource (an SR resourceillustrated in FIG. 12A) for transmitting an SR in an uplink unit bandset to terminal 200 by a separate signaling technique (for example,higher layer signaling). That is, control section 208 of terminal 200retains information related to the SR resource notified from basestation 100.

Further, terminal 200 specifies an ACK/NACK resource associated with aCCE, which is occupied by downlink assignment control informationreceived by its own terminal, among a plurality of CCEs configuringPDCCHs of downlink unit bands 1, 2, and 3 as ACK/NACK resource 1, 2, or3.

Here, in FIG. 12A, an SR resource and ACK/NACK resources 1, 2, and 3 aredifferent code resources from each other such that at least one of a ZACsequence (primary spreading) or a Walsh sequence/DFT sequence isdifferent.

Next, a description will be made in connection with mapping examples 1to 4 of the response signal in terminal 200 for suppressing the numberof SR resources to one, even when three downlink unit bands (downlinkunit bands 1 to 3) are set to terminal 200.

Mapping Example 1 FIGS. 13A and 13B

In mapping example 1, when the SR and the response signal aresimultaneously transmitted (“when SR and response signal aretransmitted” illustrated in FIG. 12C), terminal 200 decides a resource,to which the response signal is to be mapped, and a phase pointaccording to an error detection result pattern on downlink unit band 1(CC1) and downlink unit band 2 (CC2), regardless of whether or notdownlink unit band 3 (CC3) is in a state of any one of ACK, NACK, andDTX. That is, terminal 200 uses the mapping rule (FIG. 9B) used whenthere are two downlink unit bands in Embodiment 1. Here, it is assumedthat priorities, among downlink unit bands 1 to 3, which base station100 uses to transmit downlink data, are set to be higher in ascendingorder of downlink unit bands 1, 2, and 3.

Specifically, when only the response signal is transmitted (“when onlyresponse signal is transmitted” illustrated in FIG. 12B), it is similarto Embodiment 1 (FIG. 11A) as illustrated in FIG. 13A.

On the other hand, when the SR and the response signal have beensimultaneously generated (“when SR and response signal are transmitted”illustrated in FIG. 12C), reception success/failure (error detectionresult) pattern candidates of downlink unit band 1 (CC1) and downlinkunit band 2 (CC2) are associated with a phase point of the responsesignal in the SR resource as illustrated in FIG. 13B. That is, in FIG.13B, a resource for transmitting the response signal and a phase pointare decided, regardless of the reception status of downlink unit band 3(CC3) in terminal 200. That is, the response signal for downlink unitband 3 is not actually notified from terminal 200 to base station 100and dropped. That is, downlink data transmitted from base station 100 toterminal 200 using downlink unit band 3 is necessarily re-transmitted.

However, it is rare for terminal 200 side to simultaneously generate theSR and the response signal in the same sub frame. Further, even thoughbase station 100 has set three downlink unit bands for terminal 200, itis actually enough for base station 100 to transmit downlink data toterminal 200 using only one downlink unit band (for example, downlinkunit band 1 having a highest priority) in most cases, and thus basestation 100 needs not necessarily use downlink unit band 3. That is,there are few cases in which base station 100 has to transmit downlinkdata to the terminal using downlink unit band 3. When these are takeninto consideration, a possibility that terminal 200 would not detectdownlink assignment control information in downlink unit band 3 is high(that is, a possibility of DTX is high). Thus, as illustrated in FIG.13B, even though terminal 200 does not transmit (drops) informationrelated to the response signal for downlink unit band 3, retransmissionefficiency is hardly affected.

Further, when terminal 200 transmits only the SR (“when only SR istransmitted” illustrated in FIG. 12D), terminal 200 transmits the SRusing the same phase point (1, 0) as in a state (receptionsuccess/failure pattern) in which all reception statuses for downlinkunit bands 1 and 2 are NACK (or DTX) as illustrated in FIG. 13B.

Thus, in mapping example 1, only when the SR and the response signal aresimultaneously generated in the same sub frame, terminal 200 (controlsection 208) does not transmit (drops) information related to theresponse signal for some downlink unit bands (information related to theresponse signal of downlink unit band 3 in FIG. 13B). That is, only whenthe SR and the response signal are simultaneously generated in the samesub frame, terminal 200 bundles ACK for some downlink unit bands intoNACK. Here, since terminal 200 drops the response signal for thedownlink unit band having a low priority among a plurality of downlinkunit bands set to terminal 200, the dropping of some response signalsdoes not much affect retransmission efficiency. Thus, in the abovedescribed way, the overhead of the uplink control channel (PUCCH) can bereduced without lowering retransmission efficiency.

Mapping Example 2 FIGS. 14A and 14B

In mapping example 2, when the SR and the response signal aresimultaneously transmitted (“when SR and response signal aretransmitted” illustrated in FIG. 12C), terminal 200 bundles states inwhich the number of ACKs among reception success/failure (errordetection result) pattern candidates (states) is small, and the terminal200 maps a bundling result to the same phase point as the SR resource.That is, when the SR and the response signal are simultaneouslytransmitted, terminal 200 bundles reception success/failure (errordetection result) pattern candidates (states) which are relatively lowin probability of occurrence, and maps a bundling result to the samephase point as the SR resource.

Generally, base station 100 performs adaptive modulation so that anerror rate (block error rate) of downlink data can range from about 10%to about 30%. For this reason, a probability that terminal 200 willgenerate ACK as an error detection result on certain downlink data ishigher than a probability that terminal 200 will generate NACK. That is,a reception success/failure (error detection result) pattern (state)which is large in the number of ACKs is in a state in which aprobability of occurrence is relatively high, and a receptionsuccess/failure (error detection result) pattern (state) which is smallin the number of ACKs is in a state in which a probability of occurrenceis relatively low.

In this regard, when the SR and the response signal have beensimultaneously generated (“when SR and response signal are transmitted”illustrated in FIG. 12C), terminal 200 transmits a state in which thenumber of ACKs is one (a state in which the number of ACKs is small)using the same phase point (the phase point (1, 0) of the SR resource inFIG. 14B) as a state in which all is NACK (or DTX). That is, in FIG.14B, terminal 200 bundles a state in which the number of ACKs is one (astate in which the number of ACKs is small) into a state in which all isNACK (or DTX).

On the other hand, terminal 200 notifies states in which the number ofACKs is 2 or 3 (a state in which the number of ACKs is large) usingdifferent phase points in the SR resource as illustrated in FIG. 14B.Here, in order to suppress the number of SR resources to one, somestates (“N/A/A” and “D/A/A”) among states in which the number of ACKs is2 are also bundled into a state in which all is NACK (or DTX) asillustrated in FIG. 14B. Here, similarly to mapping example 1,priorities, among downlink unit bands 1 to 3, which base station 100uses to transmit downlink data, are set to be higher in ascending orderof downlink unit bands 1, 2, and 3. In this case, a state (“N (orD)/A/A”) in which the response signals for downlink unit bands 2 and 3are ACK is lower in probability of occurrence than other states(“A/A/N(or D)” and “A/N(or D)/A”) in which the number of ACKs is 2. Thatis, in FIG. 14B, in order to suppress the number of SR resources to one,some states (“N/A/A” and “D/A/A”), which are low in probability ofoccurrence, among states in which the number of ACKs is 2 are alsobundled into a state in which all is NACK (or DTX).

Thus, a state in which the number of ACKs is 1 (and some of states inwhich the number of ACKs is 2) is not actually notified from terminal200 to base station 100. That is, downlink data, which has beentransmitted from base station 100 to terminal 200 using a downlink unitband whose response signal is ACK in a state in which the number of ACKsis 1 (and some of states in which the number of ACKs is 2), isnecessarily retransmitted.

However, it is rare for terminal 200 side to simultaneously generate theSR and the response signal in the same sub frame, similarly to mappingexample 1. Further, as described above, a possibility that ACK will begenerated for certain downlink data is higher than a possibility thatNACK will be generated. When these are taken into consideration, eventhough a state in which the number of ACKs is 1 (and some of states inwhich the number of ACKs is 2), that is, a state in which a probabilityof occurrence is low, is bundled into a state in which all is NACK (orDTX), retransmission efficiency is hardly affected.

Further, in mapping example 2, when terminal 200 transmits only theresponse signal (“when only response signal is transmitted” illustratedin FIG. 12B), it is similar to Embodiment 1 (FIG. 11A) as illustrated inFIG. 14A. Further, when terminal 200 transmits only the SR (“when onlySR is transmitted” illustrated in FIG. 12D), terminal 200 transmits theSR using the same phase point (1, 0) as in the state in which all isNACK (or DTX) (and some of states in which the number of ACKs is 2), asillustrated in FIG. 14B.

In the above-described way, in mapping example 2, only when the SR andthe response signal have been simultaneously generated in the same subframe, terminal 200 (control section 208) does not transmit ACK for somedownlink unit bands. Specifically, terminal 200 (control section 208)bundles a state in which the number of ACKs is small (the state in whichthe number of ACKs is 1 in FIG. 14B) into a state in which all is NACK(or DTX). Here, since the state in which the number of ACKs is small islower in probability of occurrence than the state in which the number ofACKs is large, even though the state in which the number of ACKs issmall is bundled into the state in which all is NACK (DTX),retransmission efficiency is not much affected. Thus, in theabove-described way, the overhead of the uplink control channel (PUCCH)can be reduced without lowering retransmission efficiency.

Mapping Example 3 FIGS. 15A and 15B

In mapping example 3, when the SR and the response signal aresimultaneously transmitted (“when SR and response signal aretransmitted” illustrated in FIG. 12C), among the receptionsuccess/failure (error detection result) pattern candidates (states),terminal 200 bundles a state including ACK for downlink data transmittedusing a downlink unit band which is not important to terminal 200 into astate in which all is NACK (or DTX), and maps a bundling result to thesame phase point of the same resource. That is, when the SR and theresponse signal are simultaneously transmitted, terminal 200 does notbundle a state including ACK for downlink data transmitted using adownlink unit band which is important to terminal 200 into NACK, andperforms transmission using different phase points.

Here, examples of the downlink unit band which is important to terminal200 include (1) a downlink unit band onto which broadcast information(BCH) to be received by terminal 200 has been mapped, (2) a downlinkunit band received when terminal 200 is initially connected to basestation 100, that is, before carrier aggregation communication starts,or (3) a downlink unit band which is explicitly notified from basestation 100 to terminal 200 as an important carrier (anchor carrier). Inthe following description, it is assumed that downlink unit band 1 (CC1)is an important downlink unit band (for example, anchor carrier).

In this regard, when the SR and the response signal have beensimultaneously generated (“when SR and response signal are transmitted”illustrated in FIG. 12C), terminal 200 bundles some ACKs for downlinkunit bands 2 and 3 (unimportant downlink unit bands) other thanimportant downlink unit band 1 into NACK. On the other hand, terminal200 notifies ACK and NACK for downlink data transmitted by usingimportant downlink unit band 1 (anchor carrier, CC1), using differentphase points, as illustrated in FIG. 15B. That is, when the SR and theresponse signal have been simultaneously generated, terminal 200 decidesa resource for transmitting the response signal and a phase point, basedon only the reception status of downlink unit band 1 (CC1) independentof the reception statuses of downlink unit band 2 (CC2) and downlinkunit band 3 (CC3) in terminal 200 as illustrated in FIG. 15B.

Thus, base station 100 can reliably decide which of ACK and NACK hasbeen generated for downlink data transmitted using important downlinkunit band 1 (anchor carrier) in terminal 200. Further, when only theresponse signal is transmitted (“when only response signal istransmitted” illustrated in FIG. 12B) as illustrated in FIG. 15A, basestation 100 can decide the reception status by terminal 200 on alldownlink unit bands, similarly to Embodiment 1 (FIG. 11A).

Meanwhile, when the SR and the response signal have been simultaneouslygenerated, even though ACK has been generated in downlink unit bands 2and 3, several situations in which base station 100 is difficult todecide ACK and NACK (states notified using the phase point (1, 0)illustrated in FIG. 15B) occur.

However, similarly to mapping example 1, it is rare for terminal 200side to simultaneously generate the SR and the response signal in thesame sub frame. Further, base station 100 transmits importantinformation (for example, control information of a higher layer) usingimportant downlink unit band 1 (anchor carrier). Thus, even whenterminal 200 has simultaneously generated the SR and the responsesignal, base station 100 can reliably decide ACK and NACK for downlinkunit band 1 (anchor carrier), and terminal 200 can receive importantinformation with the small number of transmission times (the smallnumber of retransmission times). When these are taken intoconsideration, even though it is difficult to normally notify basestation 100 of information related to the response signal forunimportant downlink unit bands 2 and 3 depending on circumstances,influence on the whole system is small.

In mapping example 3, when terminal 200 transmits only the SR (“whenonly SR is transmitted” illustrated in FIG. 12D), terminal 200 transmitsthe SR using the same phase point (1, 0) as a state in which thereception status of downlink unit band 1 is NACK or DTX (that is, astate in which some ACKs of unimportant downlink unit bands 2 and 3 arebundled into NACK) as illustrated in FIG. 15B.

Thus, in mapping example 3, only when the SR and the response signalhave been simultaneously generated in the same sub frame, terminal 200(control section 208) does not transmit information related to someresponse signals for downlink unit bands (unimportant downlink unitbands) other than an important downlink unit band (anchor carrier).Specifically, terminal 200 bundles some ACKs for downlink unit bands(unimportant downlink unit bands) other than an important downlink unitband (anchor carrier) into NACK. Thus, when the SR and the responsesignal have been simultaneously generated in the same sub frame,terminal 200 preferentially notifies the response signal for theimportant downlink unit band (anchor carrier) among a plurality ofdownlink unit bands set to terminal 200. In the above described way, theoverhead of the uplink control channel (PUCCH) can be reduced withoutadversely influencing the whole system.

Mapping Example 4 FIGS. 16A and 16B

In mapping example 4, when the SR and the response signal aresimultaneously transmitted (“when SR and response signal aretransmitted” illustrated in FIG. 12C), terminal 200 decides a resourceonto which the response signal is mapped and a phase point even fromamong the ACK/NACK resource as well as the SR resource.

Specifically, in FIGS. 16A and 16B, when the SR and the response signalhave been simultaneously generated (“when SR and response signal aretransmitted” illustrated in FIG. 12C), a state in which the number ofACKs is large (here, a state in which the number of ACKs is 2 or more)is associated with a resource and a phase point which are different fromother states, similarly to mapping example 2 (FIG. 14B). That is,respective states (reception success/failure (error detection result)patterns) are associated with resources and phase points of the responsesignal, so as to prevent a state in which the number of ACKs is largefrom being bundled into other states.

Further, in FIGS. 16A and 16B, when the SR and the response signal havebeen simultaneously generated (“when SR and response signal aretransmitted” illustrated in FIG. 12C), ACK and NACK for an importantdownlink unit band (here, downlink unit band 1 (for example, anchorcarrier)) are associated with different resources and different phasepoints, similarly to mapping example 3 (FIG. 15B). That is, respectivestates (reception success/failure (error detection result) patterns) areassociated with resources and phase points of the response signal so asto prevent ACK for an important downlink unit band (here, downlink unitband 1 (for example, anchor carrier)) from being bundled into NACK.

At this time, the respective states (reception success/failure (errordetection result) patterns) are grouped into 6 types of states (6reception success/failure (error detection result) pattern candidategroups). Specifically, the respective states are grouped into 6 types ofpattern candidate groups including “A/A/A”, “A/A/N(D)”, “A/N(D)/A”,“A/N(D)/N(D)”, “N(D)/A/A”, and the other states, which are indicated bywhite circles “o” illustrated in FIGS. 16A and 16B.

In this regard, when the SR and the response signal have beensimultaneously generated (“when SR and response signal are transmitted”illustrated in FIG. 12C), terminal 200 transmits the response signalusing phase points (0, −j) of ACK/NACK resources 1 and 2 which are notused when only the response signal is transmitted (“when only responsesignal is transmitted” illustrated in FIG. 12B) among ACK/NACK resources1 and 2 illustrated in FIG. 16A in addition to 4 phase points of the SRresource illustrated in FIG. 16B. That is, terminal 200 transmitsinformation related to the response signal using a total of 6 phasepoints including 4 phase points of the SR resource illustrated in FIG.16B, and 2 phase points (0, −j) of ACK/NACK resources 1 and 2illustrated in FIG. 16A. In the above-described way, when the SR and theresponse signal have been simultaneously generated (“when SR andresponse signal are transmitted” illustrated in FIG. 12C), even thoughthere are 6 error detection result candidate pattern groups, since thephase point which is not used by the ACK/NACK resource is used, thenumber of SR resources necessary for transmitting the SR and theresponse signal can be suppressed to one.

That is, when the SR and the response signal have been simultaneouslygenerated (“when SR and response signal are transmitted” illustrated inFIG. 12C), terminal 200 bundles only a state which is a state includingACK for unimportant downlink unit bands 2 and 3 and which is small inthe number of ACKs (a state in which the number of ACKs is 1) into astate in which all is NACK (or DTX).

Thus, when the SR and the response signal have been simultaneouslygenerated (“when SR and response signal are transmitted” illustrated inFIG. 12C), base station 100 can reliably decide a state in which thenumber of ACKs is large (here, a state in which the number of ACKs is 2or more) similarly to mapping example 2, and can reliably decide theresponse signal for the important downlink unit band (for example,anchor carrier) similarly to mapping example 3.

Further, in mapping example 4, when terminal 200 transmits only theresponse signal (“when only response signal is transmitted” illustratedin FIG. 12B), it is similar to Embodiment 1 (FIG. 11A), as illustratedin FIG. 16A (black circles “”). Further, when terminal 200 transmitsonly the SR (“when only SR is transmitted” illustrated in FIG. 12D),terminal 200 transmits the SR using the same phase point (1, 0) as inthe state in which all is NACK (or DTX) (and the state including ACKdropped only when the SR is generated), as illustrated in FIG. 16B.

In the above-described way, in mapping example 4, when the SR and theresponse signal have been simultaneously generated in the same subframe, terminal 200 associates information related to the responsesignal for some downlink unit bands with the phase point which is notused by the ACK/NACK resource. As a result, the number of errordetection result pattern candidates which can be decided by the basestation can be increased, without increasing the number of SR resources.That is, the number of ACKs dropped by terminal 200 (the number of ACKsbundled into NACK) can be reduced. That is, influence on retransmissionefficiency caused by the dropping of the response signal at terminal 200side can be further reduced compared to mapping examples 2 and 3. In theabove-described way, the overhead of the uplink control channel (PUCCH)can be reduced without lowering retransmission efficiency.

The mapping examples of the response signal in terminal 200 have beendescribed above.

In the above-described way, according to the present embodiment, bydropping ACK information in some downlink unit bands at terminal 200,the overhead of the uplink control channel (PUCCH) can be furtherreduced compared to Embodiment 1.

The embodiments of the present invention have been described above.

The above embodiments have been described in connection with an examplein which all ACK/NACK resources are notified in association with CCEsoccupied by the downlink assignment control information for the terminal(that is, implicitly), however, the present invention is not limitedthereto. For example, the mapping rule of the response signal in FIG.11A may be applied to the case in which some ACK/NACK resources areexplicitly notified from the base station, as illustrated in FIGS. 17Aand 17B. FIG. 17B is identical to FIG. 11B. However, in FIG. 17A, sinceACK/NACK resource 2 is explicitly notified, the terminal side alreadyknows information of ACK/NACK resource 2 regardless of whether or notthe terminal has successfully received the downlink assignment controlinformation. Thus, the terminal can map the state such as “N/D/A” or“D/D/A” (that is, the state in which DTX has been generated for downlinkunit band 2) to ACK/NACK resource 2. That is, even when three downlinkunit bands are set to the terminal, the number of ACK/NACK resourcesnecessary for transmitting only the response signal at the terminal canbe reduced to two, compared to FIG. 11A (three ACK/NACK resources).

The above embodiments have been described in connection with the examplein which the ZAC sequence is used for primary spreading in the PUCCHresource, and the Walsh sequence and the DFT sequence are used forsecondary spreading as OC indices. However, in the present invention,non-ZAC sequences which are mutually separable by different cyclic shiftindices may be used for primary-spreading. For example, a generalizedchirp like (GCL) sequence, a constant amplitude zero auto correlation(CAZAC) sequence, a Zadoff-Chu (ZC) sequence, a pseudo-noise (PN)sequence such as an M sequence or an orthogonal gold code sequence, asequence which is randomly generated by a computer and has a steepauto-correlation characteristic on the time axis, or the like may beused for primary-spreading. The ZAC sequence may be expressed as “basesequence” in English, which means a base sequence for giving a cyclicshift. Further, sequences orthogonal to each other or any sequenceswhich are recognized as being substantially orthogonal to each other maybe used as OC indices for secondary-spreading. In the above description,a resource of a response signal (for example, a PUCCH resource) isdefined by a cyclic shift index of a ZAC sequence and a sequence numberof an OC index.

Further, the above embodiments have been described in connection withthe example in which secondary spreading is performed after primaryspreading, as an order of processing at the terminal side. However, anorder of processing of primary spreading and secondary spreading is notlimited thereto. That is, since both primary spreading and secondaryspreading are the processing represented by multiplication, for example,even when primary spreading is performed on the response signal aftersecondary spreading, the same effect as in the present embodiment isobtained.

Further, the above embodiments have been described in connection withthe example in which control section 101 of base station 100 performscontrol such that downlink data and downlink assignment controlinformation for the downlink data are mapped to the same downlink unitband, however, the present embodiment is not limited thereto. That is,even when downlink data and downlink assignment control information forthe downlink data are mapped to separate downlink unit bands, thepresent embodiment can be applied as long as a correspondence relationbetween the downlink assignment control information and the downlinkdata is clear. In this case, the terminal side obtains ACK/NACK resource1 as a PUCCH resource corresponding to “a resource (CCE) occupied bydownlink assignment control information for downlink data transmittedthrough downlink unit band 1.”

Further, the above embodiments have been described in connection withthe example in which the response signal transmitted by the terminal ismodulated using a quadrature phase shift keying (QPSK) scheme. However,the present invention is not limited to the case in which the responsesignal is modulated using the QPSK scheme and can be applied, forexample, even when the response signal is modulated using the BPSKscheme or a 16 quadrature amplitude modulation (QAM).

Further, the above embodiments have been described in connection withthe example in which the present invention is implemented in hardware,however, the present invention may be implemented in software.

The functional blocks used for description of the above embodiments aretypically implemented as large scale integration (LSI) which is anintegrated circuit (IC). The functional blocks may be individuallyimplemented as one chip, or some or all of the functional blocks may beimplemented as one chip. Here, “LSI” is adopted here but this may alsobe referred to as “IC,” “system LSI,” “super LSI” or “ultra LSI”depending on a difference in integration.

A circuit integration technique is not limited to the LSI, andimplementation by a dedicated circuit or a universal processor may beadopted. After LSI manufacture, a field programmable gate array (FPGA)which is programmable or a reconfigurable processor in which connectionsand settings of circuit cells within an LSI can be reconfigured may beused.

Further, if a circuit integration technique of replacing the LSI byanother technique advanced or derived from a semiconductor technologyappears, the functional blocks may be integrated using the technique.There may be a possibility that a biotechnology will be applied.

The disclosure of Japanese Patent Application No. 2009-230727, filed onOct. 2, 2009, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

A terminal apparatus and a retransmission method according to thepresent invention are useful in simultaneously transmitting an SR and aresponse signal while suppressing an increase in the overhead of anuplink control channel, when channel selection is applied as a method oftransmitting a response signal when carrier aggregation communication isperformed using a plurality of downlink unit bands.

REFERENCE SIGNS LIST

-   100 Base station-   101 Control section-   102 Control information generating section-   103, 105 Coding section-   104, 107, 213 Modulating section-   106 Data transmission control section-   108 Mapping section-   109, 216 IFFT section-   110, 217 CP adding section-   111, 218 Radio transmitting section-   112, 201 Radio receiving section-   113, 202 CP removing section-   114 PUCCH extracting section-   115 Despreading section-   116 Sequence control section-   117 Correlation processing section-   118 Deciding section-   119 Retransmission control signal generating section-   200 Terminal-   203 FFT section-   204 Extracting section-   205, 209 Demodulating section-   206, 210 Decoding section-   207 Deciding section-   208 Control section-   211 CRC section-   212 Response signal generating section-   214 Primary spreading section-   215 Secondary spreading section

1. A base station communicating with a terminal configured with one ormore downlink component carriers, the base station comprising: atransmitting section configured to transmit, to the terminal, downlinkassignment information indicating a resource for downlink data, theresource being assigned to respective ones of the downlink componentcarriers, and configured to transmit the downlink data to the terminal;a receiving section configured to receive a response signal for thedownlink data, the response signal being transmitted from the terminal,and to receive a scheduling request (SR), which is transmitted from theterminal, wherein: the response signal denotes an outcome of a decodingof the downlink data, or denotes a Discontinuous Transmission (DTX)representing that the outcome is not transmitted; when a plurality ofdownlink component carriers are configured, response signals for aplurality of downlink data in the downlink component carriers aretransmitted; when the response signals are transmitted, the responsesignals are transmitted using a phase point and one of uplink controlchannel resources for the response signals depending on an outcome ofthe decoding of each of the plurality of downlink data; and when boththe response signals and the SR are transmitted in a same sub-frame, theresponse signals are transmitted using the phase point and an uplinkcontrol channel resource for the SR depending on an outcome of thedecoding of each of the plurality of downlink data.
 2. The base stationaccording to claim 1, wherein when both the response signals and the SRare transmitted in the same sub-frame, a same phase point is used forthe response signals that each denotes an unsuccessful outcome of thedecoding or the DTX.
 3. The base station according to claim 1, whereinwhen both the response signals and the SR are transmitted in the samesub-frame, a same phase point is used for different combinations of theresponse signals that share a same number of one or more responsesignals denoting a successful outcome of the decoding and that alsoshare a same downlink component carrier in which the downlink data aresuccessfully decoded.
 4. The base station according to claim 1, whereinwhen both the response signals and the SR are transmitted in the samesub-frame, at least some of the response signals are bundled into oneresponse signal.
 5. The base station according to claim 1, wherein whenboth the response signals and the SR are transmitted in the samesub-frame, the phase point used for the response signals that eachdenotes an unsuccessful outcome of the decoding or the DTX is the sameas the phase point used for the response signals, one of which denotes asuccessful outcome of the decoding.
 6. The base station according toclaim 1, wherein the transmitting section is configured to transmit thedownlink assignment information on a control channel element (CCE), andan index of the uplink control channel resource for the response signalis associated with a CCE number.
 7. The base station according to claim1, wherein the transmitting section is configured to transmit thedownlink assignment information on a control channel element (CCE), anindex of the uplink control channel resource for the response signal isassociated with a CCE number, and the base station is further configuredto signal an index of the uplink control channel resource for the SR. 8.The base station according to claim 1, wherein the transmitting sectionis configured to transmit the downlink assignment information on acontrol channel element (CCE), an index of the uplink control channelresource for the response signal is associated with a CCE number, and anindex of the uplink control channel resource for the SR is configured bya higher layer.
 9. The base station according to claim 1, wherein theoutcome of the decoding is denoted by an Acknowledgement (ACK) or aNegative Acknowledgment (NACK).
 10. The base station according to claim1, wherein the DTX represents that the downlink assignment informationfor the downlink data is not detected at the terminal.
 11. The basestation according to claim 1, wherein the phase point is a phase pointin a binary phase shift keying (BPSK) modulation or in a quadraturephase shift keying (QPSK) modulation.
 12. The base station according toclaim 1, wherein a combination of outcomes of the decoding of theplurality of downlink data is associated with the phase point and anindex of the uplink control channel resource for the response signal.13. The base station according to claim 12, wherein differentcombinations are respectively associated with different phase points anddifferent resource indexes of the uplink control channel resources forthe response signal.
 14. A method for receiving a response signaltransmitted from a terminal configured with one or more downlinkcomponent carriers, the method comprising: transmitting, to theterminal, downlink assignment information indicating a resource fordownlink data, the resource being assigned to respective ones of thedownlink component carriers, and transmitting the downlink data to theterminal; receiving a response signal for the downlink data, theresponse signal being transmitted from the terminal; and receiving ascheduling request (SR), which is transmitted from the terminal,wherein: the response signal denotes an outcome of a decoding of thedownlink data, or denotes a Discontinuous Transmission (DTX)representing that the outcome is not transmitted; when a plurality ofdownlink component carriers are configured, response signals for aplurality of downlink data in the downlink component carriers aretransmitted; when the response signals are transmitted, the responsesignals are transmitted using a phase point and one of uplink controlchannel resources for the response signals depending on an outcome ofthe decoding of each of the plurality of downlink data; and when boththe response signals and the SR are transmitted in a same sub-frame, theresponse signals are transmitted using the phase point and an uplinkcontrol channel resource for the SR depending on an outcome of thedecoding of each of the plurality of downlink data.